<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta http-equiv="X-UA-Compatible" content="IE=edge">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>天气案例_深度监视</title>
    <script type="text/javascript" src="../js/vue.js"></script>
</head>
<body>
    <div id="root">
        <h2>今天天气很{{info}}</h2>
        <button @click="changeMeather">切换天气</button>
        <hr/>
        <h3>a的值是：{{number.a}}</h3>
        <button @click="number.a++">点我让a+1</button>
        <h3>b的值是：{{number.b}}</h3>
        <button @click="number={a:888,b:666}">彻底替换number</button>
    </div>
</body>
<script type="text/javascript">
    Vue.config.productionTip=false;
    const vm=new Vue({
        el:'#root',
        data:{
            isHot:true,
            number:{
                a:1,
                b:1
            }
        },computed: {
            info(){
               return this.isHot?'炎热':'凉爽'
            }
        },
        methods: {
            changeMeather(){
                this.isHot=!this.isHot
            }
        },
        watch:{
            isHot:{
                //immediate:true, //初始化时让handler调用一下
                //handler调用：当isHot发生改变时
                handler(newValue,oldValue){
                    console.log('isHot被修改了',newValue,oldValue)
                }
            },

            //监视多级结构中某个属性的变化
            // 'number.a':{
            //     handler(){
            //         console.log('a被改变了')
            //     }
            // },

            //监视多级结构中所有属性的变化
            number:{
                deep:true,
                handler(){
                    console.log('number改变了')
                }
            }
        }
    })
</script>
</html>